Almost any plant which produces seeds can be grown from seed, though the requirements for a number of them, some of them, are extraordinary. Germination period of two years is necessary for particular shrub seeds; extended cold spells necessary to get a dormancy that needs to precede germination for some seeds may lead to failure if omitted.
A couple of seeds, such as pine seeds for example, must never be permitted to get dry or they will not be viable; and a few should have light to germinate. Generally speaking, however, decent soil, enough heat, some moisture, and a cautious patting of the soil around the seeds will indicate they will come up and start new plants for you. As soon as they’re up, they need to be protected in the fungus disease,”damping off,” particularly if grown indoors or in a greenhouse. And though it’s moisture that causes this fungus to flourish, plus lack of air flow, the young plant shouldn’t be permitted to dry out.
There’s an interdependence of carefully placed young plants, possibly through a sharing of water and possibly through mutual advantages from root exudates, so avoid isolating them. Nevertheless they shouldn’t be crowded for long. If the soil is quite loose and partly dry, it’s possible to pull up the weaker plants in a row or in an apartment or peat pot. But the best advice isn’t to do it. It’s much better to take a small pair of sharp scissors and snip off the weak and crowding plant at ground level. The remaining small plants will remain strong and grow more powerful, particularly if they continue their interdependence.
Most seed packets tell you what distances you need to thin your crops. Initially the space always seems too fantastic. When confronted with two or three-inch plants, it appears almost wasteful to lean them to eight inches apart. But do what the package says. They’ll need that space when they grow; and the sources of soil nutrients available to the young plants in an uncrowded space imply that they’ll grow all that much better.
Indoor Seed Planting
There are two absolute necessities for developing good little plants inside to set out on your backyard later – or maybe route through a cold frame and then set our in the backyard. The first is to get good seeds out of a fantastic reliable seedsman (or use the best of your home-grown seeds). The second is to get a set-up which will offer the ideal heat, moisture, air and light for small plants.
Most of the seeds you may grow for backyard flowers or other ornamentals will be more or less fresh seeds, but the purpose is for them to become workable, or capable of germinating. Some you collect yourself you may keep for many years. The seeds of asters will keep a year or up to 13 years, depending upon the variety. Bee balm seeds will stay viable for four to seven years; nasturtiums for five to eight decades.
If you save the seeds of azaleas, birches, deutzia, hydrangeas, mock orange, potentillas and rhododendrons, by way of instance, you don’t have to put them through a cold period, but other plants do require a cold dormancy: walnut seeds should get three weeks of cold, either outside or in the fridge; barberry seeds need a few months, bittersweet seeds require three weeks, as do flowering dogwood, ash, beech, sweetgum, tupelo and a lot of the members of the Prunas group, such as cherries. Pijnboom seeds need 2 months; spruce one to three months and apples one to three months also.